Conventional processes for forming silicon nitride spacers typically result in under etching of a silicon nitride layer or over etching of underlying silicon containing layers of a substrate. Under etching of the silicon nitride layer may leave excess material proximate a gate stack/silicon layer interface (e.g., “foot” formation), thereby resulting in a poorly defined interface that may lead to a degradation in device performance. Over etching of an underlying silicon containing layer may reduce a thickness of the silicon containing layer to an extent that the silicon containing layer may fully amorphize during subsequent processes thereby leading to device failure.
Accordingly, the inventors have provided an improved method for forming silicon nitride spacers.